In recent years, in the connection between boards, between computers, between peripheral devices and so on, problems such as delay of signals, generation of heat, generation of EMI (electromagnetic noise) and so on due to electrical wiring are coming to surface. For solving these problems that occur in the electrical wiring, optical interconnection that uses silicon photonics techniques is being developed (refer to Non-patent-related Documents 1, 2, and 3). In this regard, it is interpreted that the silicon photonics means an optical device technique that uses silicon as a material, and that the optical interconnection means a technique for communicating signals by converting an electric signal from an external device to an optical signal and/or converting an optical signal to an electric signal, and transmitting the optical signal or the electric signal to another external device or the like. The optical interconnection is an innovative technique for eliminating problems relating to the electrical wiring, such as delay of a signal due to parasitic capacitance, deterioration of signal due to instable grounding, EMI radiation from an electrical line and so on. However, specifications of the constructions for inputting/outputting optical signals and electric signals and so on are often unique to the constructions respectively, that is, the specifications are not standardized.
For realizing the optical interconnection, some suggestions regarding a photoelectric hybrid device that mixedly loads optical circuits and electronic parts on a circuit board have been proposed (for example, refer to the “Background Art” section of Patent-related Document 1, FIG. 13 of Patent-related Document 2, etc.).
For example, regarding a device relating to a chip-type optical transceiver using a silicon photonics, a silicon photo-chip provided from Luxtera, that is installed on a printed circuit board (PCB) available from Molex, is available. The silicon photo-chip is an optical transceiver (refer to page 11 of Non-patent-related Document 3), and it is constructed in such a manner that an electric signal and an optical signal are to be inputted into and outputted from the upper surface of the chip. The silicon photo-chip of Luxtera and the PCB of Molex are electrically connected by wire-bonding; and optical fibers for communicating optical signals are directly adhered to the top part of a silicon CMOS chip by use of an epoxy resin (refer to Non-patent-related Document 2).
In prior art, as an elemental technology for fabricating a photoelectric hybrid device, a technique of a self-forming optical waveguide has been known. In the self-forming optical waveguide technique, by allowing light having a photosensitive wavelength for a photocurable resin to propagate through the resin, a part in the resin through which the light propagated is cured and made to be an optical waveguide core (for example, refer to Patent-related Document 2). An example implementation of a photoelectric hybrid device 29400, which may be fabricated by use of such a prior-art self-forming optical waveguide technique, is shown in FIG. 32. A photodetector 29450 is placed on a substrate 29410 in such a manner that the light receiving surface of the photodetector 29450 faces upward. An optical waveguide core 29420, which may be made of photocurable resin, is formed on the top part of the photodetector 29450 in such a manner that the optical waveguide core 29420 is vertical to the substrate 29410 and extends upwardly from the light receiving surface of the photodetector 29450. The part around the optical waveguide core 29420 is covered by a resin that acts as a clad layer 29430. A 45-degree mirror 29460 is placed above the upper end surface of the optical waveguide core 29420, and an optical fiber 29470 is placed at a position that is above the clad layer 29430 and beside the 45-degree mirror 29460. In such an implementation, an optical path of an optical signal that has been transmitted via the optical fiber 29470 is vertically bended by the 45-degree mirror 29460 toward the substrate 29410. As a result, the optical signal enters the optical waveguide core 29420 and propagates therethrough, and the photodetector 29450 receives the propagated optical signal.
FIGS. 33A and 33B illustrate an example of a method for fabricating the optical waveguide core 29420 formed of a photocurable resin (refer to FIG. 2 of Patent-related Document 2). First, a photocurable resin 29422 is supplied onto the substrate 29410 (the photodetector is not shown), and a mask 29510 for forming an optical waveguide core is placed on the photocurable resin 29422. The mask 29510 comprises a glass plate 29514 and a chrome film 29516 formed on one of the surfaces of the glass plate 29514 except for an area for an opening 29512. Next, the photocurable resin 29422 is irradiated by a light 29520 having a photosensitive wavelength for the photocurable resin 29422 (for example, UV light) via the mask 29510 (FIG. 33A). By the light passing through the opening 29512 and propagating through the photocurable resin, a part of the photocurable resin through which the light propagates is cured and the optical waveguide core 29420 is consequently formed (FIG. 33B). Next, an uncured portion of the photocurable resin 29422 is washed and removed by a developing solution. Further, a resin 29430 for a clad layer is filled in the space around the optical waveguide core 29420.